Core fucose is critical for CD14-dependent Toll-like receptor 4 signaling

Area of Science:

• Glycobiology
• Immunology
• Cell Biology

Background:

• Core fucosylation, a posttranslational modification of N-glycans, affects growth factor receptor function.
• Core-fucose-deficient mice (Fut8 knockout) show pulmonary emphysema and impaired macrophage function, resembling aged Toll-like receptor 4 (TLR4)-deficient mice.

Purpose of the Study:

• To investigate the role of core fucosylation in the Toll-like receptor 4 (TLR4) signaling pathway.
• To determine how the absence of core fucose impacts TLR4-mediated immune responses.

Main Methods:

• Utilized Fut8-deficient mouse embryonic fibroblasts (MEFs) and wild-type MEFs.
• Stimulated cells with lipopolysaccharide (LPS).
• Analyzed cytokine production (interleukin-6, interferon-beta) and TLR4 signaling complex components via lectin blot and assessed receptor internalization.

Main Results:

• Fut8-deficient MEFs produced similar levels of IL-6 but significantly reduced IFN-β compared to wild-type MEFs after LPS stimulation.
• Core fucosylation was specifically detected on CD14 within the TLR4 signaling complex.
• While TLR4/MD-2 activation and dimerization were unaffected, the internalization of TLR4 and CD14 was significantly impaired in Fut8-deficient cells.

Conclusions:

• Core fucosylation is critical for the proper internalization of the TLR4/MD-2 complex.
• Impaired TLR4/MD-2 internalization due to lack of core fucose leads to reduced IFN-β production.
• This study demonstrates a novel regulatory role of glycosylation in TLR4 signaling.